The object of this proposal is to test the feasibility and to construct a 100 KeV scanning transmission Proton Microscope for the purpose of investigating organic structures, ultimately with resolution of the order of atomic dimensions. The realization of this new instrument entails the use of field ionization to provide a point-like source of protons. The overall design is otherwise very close to that of Crewe's high resolution scanning electron microscopes. Experiments are under way to explore the performance of a field ionization tip used as a beam source. An operational scanning electron gun-microscope is being modified for this purpose, to incorporate a liquid helium cryostat for tip cooling. A Butler-type accelerating gun will focus the extracted proton beam. The ultimate design of the microscope, depending on the results obtained in the gun microscope, will involve the use of a high field superconducting lens, chromatic aberration correctors and proton spectrometer. The interaction of protons with the specimen makes available to image formation an additional contrast mechanism to those in common with the electron microscope; the charge exchange process. The latter exhibits the unique feature of being sensitive to the hydrogen concentration in the specimen.